am I insane?

first of all, sorry for the long post but i need to vent a little. I fell in love with a man over twice my age. When I first met him, I was taking care of his mother, who had dementia. I thought he was a funny guy, just uplifting to be around. But once I'd walk his mother to bed we'd sit around and talk about everything. Life and love and just everything. I found myself opening up to him, like I never have been able to with anyone else. We stood out on the porch smoking, looking up at the stars. Id show him constellations and  he'd listen and ask questions. One evening when I was getting ready to go home, he asked me if I would like to join him for supper, I told him I'd like that. He cooked steaks and sweet potatoes on the grill for us and set up a table on his deck and we drank a few beers and he admitted he thought he was falling for me. I admitted the same. It's been a year and I'm so scared. I've always been afraid to get too close, because it always ends--whether it be the fact that you grow apart, one cheats on the other, or death. And death is the scariest one because you can't text them to say you miss them, you can't call to say I was wrong. He's over twice my age but I love him so much. He's shown me how a man is supposed to treat a woman. I've never been treated that way..all the boys I've dated only cared about what they could get out of me. He was married for 18 years, his ex cheated on him, married a guy 6 months later and divorced  him 5 years later. I can't understand how someone would throw away someone so special, when I would give anything to have those years as my own. I know this will break my heart in the end but I can't walk away from him. I can't break his heart because it'll break mine.